I have bit the bullet and am having my M700 rebarreled to 22-243 Middlestead.
However, I have never had to do fireforming, etc. Can anybody explain the process for this cartridge and what I will need in terms of dies, etc?

Do yourself a favor and just chamber to 22-243 (plain) no fireforming of any kind. Just take a Lapua 243 case and neck it down and you're done. I really don't see the advantage of the Middlestead. I've owned a 22-243AI and the non-AI version.

Fireforming wastes valuable (and limited) case life in the cartridge.

You didn't mention what barrel twist you were getting but I'd suggest nothing slower than an 8 twist. You really can't get the full potential out of this cartridge without using one of the heavy, high BC bullets which require a fast twist barrel. You could shoot 52-55gr bullets out of the fast twist if you wanted to but you can't shoot the heavy bullets out of a slow twist.